Upgrading existing coal-fired power plants through heavy-duty and aeroderivative gas turbines

The need to meet future changes in power demand and current environmental regulations are considered the main driving forces for upgrading existing coal-fired power plants. In this context, repowering by gas-turbine integration is a well-established technique to increase power plant capacity and operational flexibility. Non-negligible benefits are also improvements in efficiency and a decrease in greenhouse gases emissions promoted by the shift to low carbon fuels. This paper aims to investigate the impact of feedwater heater repowering on a 300MW coal-fired power plant. Marginal efficiency and power increase, as well as the performance of integrated steam-gas power plants, are evaluated by varying the steam section operating conditions and gas turbine technology. Three main cases are investigated, assuming integration with simple or regenerative heavy-duty gas turbines and aeroderivative gas turbines. As part of this investigation, a performance plane is defined, allowing to compare repowering options based on different steam turbine overloads and boiler modes of operation. Focusing on repowering configurations with the maximum power increase, the analysis also examines the plant capability to follow potential load variations and their impact on energy and economic performance parameters.